The present invention relates to a winding core for a coil winding device.
When a wire is bent into a generally square shape or any other polygonal shape in winding the wire around a winding core of a winder to form a coil, the wire is sprung back from the intended bending angle. In the coil winding device disclosed in Japanese Patent Application Publication No. 2010.4589, the winding core of the winder is formed helically with the springback taken into previous consideration. More specifically, the winding core includes four core bars each having a substantially rectangular cross-section with four rounded corners and the wire is wound around the winding core for N times (N is an integer of two or more) to form a coil. The winding core has winding tracks forming N steps for winding wire and the winding tracks are formed such that each four corners of the winding tracks are circumferentially deviated every step to make the winding core into a helical shape.
Referring to FIG. 9A showing the background art according to the above-cited Publication No. 2010-4589, the helical winding core 100 has winding tracks 101, 102, 103, 104 and a step is formed between any two adjacent winding tracks, as shown in FIG. 9A. Each of the winding tracks 101, 102, 103, 104 has a contacting surface with which the wire (flat wire) 110 is in perpendicular contact. The wire 110 is pressed against the winding core 100 by the guide member 120 of a pressing roller. The wire 110 pressed against the step by the guide member 120 is moved to the adjacent step formed between the winding tracks 101, 102, 103, 104, so that the wire 110 is damaged by the step. For preventing the above damage to the wire 110, the winding tracks 101, 102, 103, 104 may be widened or the width W of the winding tracks 101, 102, 103, 104 may be increased, as shown in FIG. 9B so that the wire 110 is not moved to the adjacent step. However, widening the tracks 101, 102, 103, 104 widens the clearance between any two adjacent turns of the wire in the axial direction of the winding core 100 and increases the total length of the coil.
The present invention is directed to providing a winding core for a coil winding device by which damage to a wire hardly occurs and an increase of the total length of wound coil is prevented.